3D Printing of Personalised Carvedilol Tablets Using Selective Laser Sintering.

Selective laser sintering (SLS) has drawn attention for the fabrication of three-dimensional oral dosage forms due to the plurality of drug formulations that can be processed. The aim of this work was to employ SLS with a CO2 laser for the manufacturing of carvedilol personalised dosage forms of various strengths. Carvedilol (CVD) and vinylpyrrolidone-vinyl acetate copolymer (Kollidon VA64) blends of various ratios were sintered to produce CVD tablets of 3.125, 6.25, and 12.5 mg. The tuning of the SLS processing laser intensity parameter improved printability and impacted the tablet hardness, friability, CVD dissolution rate, and the total amount of drug released. Physicochemical characterization showed the presence of CVD in the amorphous state. X-ray micro-CT analysis demonstrated that the applied CO2 intensity affected the total tablet porosity, which was reduced with increased laser intensity. The study demonstrated that SLS is a suitable technology for the development of personalised medicines that meet the required specifications and patient needs.

3D Printed Flavor-Rich Chewable Pediatric Tablets Fabricated Using Microextrusion for Point of Care Applications.

Over the past few years, 3D printing technologies have gained interest in the development of medicinal products for personalized use at the point of care. The printing of drug products offers personalization and flexibility in dose, shape/design, and flavor, potentially enhancing acceptability in pediatric populations. In this study, we present the design and development of ibuprofen (IBU) chewable flavor-rich personalized dosage forms by using microextrusion for the processing of powdered blends. The optimization processing parameters such as applied pneumatic pressure and temperature resulted in high quality printable tablets of various designs with a glossy appearance. Physicochemical characterization of the printed dosages revealed that IBU was molecularly dispersed in the methacrylate polymer matrix and the formation of H bonding. A panelist's study demonstrated excellent taste masking and aroma evaluation when using strawberry and orange flavors. Dissolution studies showed very fast IBU dissolution rates of more than 80% within the first 10 min in acidic media. Microextrusion is a 3D printing technology that can be effectively used to generate pediatric patient centric dosage forms at the point of care.

Amorphous Drug-Polymer Salts: Maximizing Proton Transfer to Enhance Stability and Release.

An amorphous drug-polymer salt (ADPS) can be remarkably stable against crystallization at high temperature and humidity (e.g., 40°C/75% RH) and provide fast release. Here, we report that process conditions strongly influence the degree of proton transfer (salt formation) between a drug and a polymer and in turn the product's stability and release. For lumefantrine (LMF) formulated with poly(acrylic acid) (PAA), we first show that the amorphous materials prepared by slurry conversion and antisolvent precipitation produce a single trend in which the degree of drug protonation increases with PAA concentration from 0% for pure LMF to ∼100% above 70 wt % PAA, independent of PAA's molecular weight (1.8, 450, and 4000 kg/mol). This profile describes the equilibrium for salt formation and can be modeled as a chemical equilibrium in which the basic molecules compete for the acidic groups on the polymer chain. Relative to this equilibrium, the literature methods of hot-melt extrusion (HME) and rotary evaporation (RE) reached much lower degrees of salt formation. For example, at 40 wt % drug loading, HME reached 5% salt formation and RE 15%, both well below the equilibrium value of 85%. This is noteworthy given the common use of HME and RE in manufacturing amorphous formulations, indicating a need for careful control of process conditions to ensure the full interaction between the drug and the polymer. This need arises due to the low mobility of macromolecules and the mutual hindrance of adjacent reaction sites. We find that a high degree of salt formation enhances drug stability and release. For example, at 50% drug loading, an HME-like formulation with 19% salt formation crystallized faster and released only 20% of the drug relative to a slurry-prepared formulation with 70% salt formation. Based on this work, we recommend slurry conversion as the method for preparing ADPS for its ability to enhance salt formation and continuously adjust drug loading. While this work focused on salt formation, the impact of process conditions on the molecular-level interactions between a drug and a polymer is likely a general issue for amorphous solid dispersions, with consequences on product stability and drug release.

Kinetics of Surface Enrichment of a Polymer in a Glass-Forming Molecular Liquid.

X-ray photoelectron spectroscopy has been used to measure the surface concentration and the surface enrichment kinetics of a polymer in a glass-forming molecular liquid. As a model, the bulk-miscible system of maltitol-polyvinylpyrrolidone (PVP) was studied. The PVP concentration is significantly higher at the liquid/vapor interface than in the bulk by up to a factor of 170, and the effect increases with its molecular weight. At a freshly created liquid/vapor interface, the concentration of PVP gradually increases from the bulk value at a rate controlled by bulk diffusion. The polymer diffusion coefficient obtained from the kinetics of surface enrichment agrees with that calculated from viscosity and the Stokes-Einstein equation. Our finding allows prediction of the rate at which the surface composition equilibrates in an amorphous material after milling, fracture, and a change in ambient temperature.

Personalised paediatric chewable Ibuprofen tablets fabricated using 3D micro-extrusion printing technology.

Three-dimensional (3D) printing is becoming an attractive technology for the design and development of personalized paediatric dosage forms with improved palatability. In this work micro-extrusion based printing was implemented for the fabrication of chewable paediatric ibuprofen (IBU) tablets by assessing a range of front runner polymers in taste masking. Due to the drug-polymer miscibility and the IBU plasticization effect, micro-extrusion was proved to be an ideal technology for processing the drug/polymer powder blends for the printing of paediatric dosage forms. The printed tablets presented high printing quality with reproducible layer thickness and a smooth surface. Due to the drug-polymer interactions induced during printing processing, IBU was found to form a glass solution confirmed by differential calorimetry (DSC) while H-bonding interactions were identified by confocal Raman mapping. IBU was also found to be uniformly distributed within the polymer matrices at molecular level. The tablet palatability was assessed by panellists and revealed excellent taste masking of the IBU's bitter taste. Overall micro-extrusion demonstrated promising processing capabilities of powder blends for rapid printing and development of personalised dosage forms.

Superiority of Mesoporous Silica-Based Amorphous Formulations over Spray-Dried Solid Dispersions.

The aim of this study was to compare the performance of two amorphous formulation strategies: mesoporous silica via solvent impregnation, and solid dispersions by spray drying. Poorly soluble fenofibrate was chosen as the model drug compound. A total of 30% Fenofibrate-loaded mesoporous silica and spray-dried solid dispersions (SDD) were prepared for head-to-head comparisons, including accelerated stability, manufacturability, and in vitro biorelevant dissolution. In the accelerated stability study under 40 °C/75% RH in open dish, mesoporous silica was able to maintain amorphous fenofibrate for up to 3 months based on solid-state characterizations by PXRD and DSC. This result was superior compared to SDD, as recrystallization was observed within 2 weeks. Under the same drug load, fenofibrate-loaded mesoporous silica showed much better flowability than fenofibrate-loaded SDD, which is beneficial for powder handling of the intermediate product during the downstream process. The in vitro 2-stage dissolution results indicated a well-controlled release of fenofibrate from mesoporous silica in the biorelevant media, rather than a burst release followed by fast precipitation due to the recrystallization in the early simulated gastric phase for SDD. The present study demonstrates that mesoporous silica is a promising formulation platform alternative to prevailing spray-dried solid dispersions for oral drug product development.

Surface Enrichment of Surfactants in Amorphous Drugs: An X-ray Photoelectron Spectroscopy Study.

Surfactants are commonly incorporated into amorphous formulations to improve the wetting and dissolution of hydrophobic drugs. Using X-ray photoelectron spectroscopy, we find that a surfactant can significantly enrich at the surface of an amorphous drug, up to 100% coverage, wihout phase separation in the bulk. We compared four different surfactants (Span 80, Span 20, Tween 80, and Tween 20) in the same host acetaminophen and the same surfactant Span 80 in four different hosts (acetaminophen, lumefantrine, posaconazole, and itraconazole). For each system, the bulk concentrations of the surfactants were 0, 1, 2, 5, and 10 wt %, which cover the typical concentrations in amorphous formulations, and component miscibility in the bulk was confirmed by differential scanning calorimetry. For all systems investigated, we observed significant surface enrichment of the surfactants. For acetaminophen containing different surfactants, the strongest surface enrichment occurred for the most lipophilic Span 80 (lowest HLB), with nearly full surface coverage. For the same surfactant Span 80 doped in different drugs, the surface enrichment effect increases with the hydrophilicity of the drug (decreasing log P). These effects arise because low-surface-energy molecules (or molecular fragments) tend to enrich at a liquid/vapor interface. This study highlights the potentially large difference between the surface and bulk compositions of an amorphous formulation. Given their high mobility and low glass transition temperature, the surface enrichment of surfactants in an amorphous drug can impact its stability, wetting, and dissolution.

Investigation on hot melt extrusion and prediction on 3D printability of pharmaceutical grade polymers.

The development of printable filaments has been identified as a critical aspect for the processing of pharmaceutical grade polymers and the fabrication of oral solid dosage forms. In this study a range of plain and drug loaded polymers were investigated and assessed for their printability in comparison to commercial filaments. Physicochemical characterizations of the polymers included differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and rheology were studied prior to Hot Melt Extrusion processing for the filament fabrication. A texture analyser was used to study the filament mechanical properties in order to derive the maximum tensile strength, Young's Modulus and elongation at break. Principal component analysis was used to compare the printability of the polymer and to identify the contribution of each mechanical property. The analysis showed that maximum tensile strength with a threshold between 15 and 20 MPa is the most critical property for the prediction of the printability. Furthermore, printable filaments were processed using Fusion Deposition Modelling technology and optimal printing parameters were identified. The study demonstrated that the prediction of filament printability is feasible by evaluating the mechanical properties.

3D printed bilayer tablet with dual controlled drug release for tuberculosis treatment.

In this study Fusion Deposition Modelling (FDM) was employed to design and fabricate a bilayer tablet consisting of isoniazid (INZ) and rifampicin (RFC) for the treatment of tuberculosis. INZ was formulated in hydroxypropyl cellulose (HPC) matrix to allow drug release in the stomach (acidic conditions) and RFC was formulated in hypromellose acetate succinate (HPMC - AS) matrix to allow drug release in the upper intestine (alkaline conditions). This design may offer a better clinical efficacy by minimizing the degradation of RFC in the acidic condition and potentially avoid drug-drug interaction. The bilayer tablet was prepared by fabricating drug containing filaments using hot melt extrusion (HME) coupled with the 3D printing. The HME and 3D printing processes were optimised to avoid drug degradation and assure consistent deposition of drug-containing layers in the tablet. The in-vitro drug release rate was optimised by varying drug loading, infilling density, and covering layers. Greater than 80% of INZ was released in 45 mins at pH 1.2 and approximately 76% of RFC was releases in 45 mins after the dissolution medium was changed to pH 7.4. The work illustrated the potential application of FDM technology in the development of oral fixed dose combination for personalised clinical treatment.

A preliminary assessment of the impact of hot-melt extrusion on the physico-mechanical properties of a tablet.

OBJECTIVES: This research aimed at investigating the difference between the powders prior to and after hot melt extrusion. A preliminary assessment was also conducted to gain a better mechanistic understanding of the impact of hot melt extrusion on tabletability. MATERIALS AND METHODS: Kollidon® VA 64 and mannitol were sieved into different particles sizes and used as is or after drying for 24 h. Hot melt extrusion was used to manufacture an amorphous solid dispersion of Kollidon® VA 64 and mannitol. The extrudates were milled and sieved into different particles sizes. Tablets were manufactured from the different powders and their tabletability, compressibility and compactibility determined. RESULTS AND DISCUSSIONS: It was shown that the as received tablets gave higher tabletability compared with the tablets manufactured from the dried or hot melt extruded (HME) powder. Differences in the tabletability between the as received. dried and HME material could be related back to changes in the bonding area and bonding strength as a result of the hot melt extrusion process and/or a loss of moisture because of the high processing temperature. CONCLUSIONS: The reduced tabletability of the HME tablets appeared to be a function of multiple factors. Both the hot melt extrusion process and the moisture content may play significant roles in determining this phenomenon.

Evaluation of different screening methods to understand the dissolution behaviors of amorphous solid dispersions.

OBJECTIVE: The objectives of the current study were to understand the dissolution behaviors of amorphous solid dispersions (ASD) using different screening methods and their correlation to the dissolution of formulated products. MATERIALS AND METHODS: A poorly soluble compound, compound E, was used as a model compound. ASDs were prepared with HPMC, Kollidon VA64 and Eudragit EPO using hot-melt extrusion. Different techniques including precipitation, powder, capsule and compact dissolution and the dissolution of formulated products were conducted in USP simulated gastric fluid using a USP II dissolution apparatus. RESULTS AND DISCUSSIONS: It was found that a precipitation study could generally predict powder, capsule and compact dissolution. Yet, it was recommended to run the dissolution at a higher paddle speed or for a longer duration to improve the predictability. It was also recommended to run powder, capsule and compact dissolution at both slow and high speeds to gain insights into wetting, dispersion and the dissolution of a system. Sometimes, capsule or compact dissolution could not be predicted by precipitation or powder dissolution due to plug formation. In this case, properly designed dosage forms were needed to break up this plug to optimize the dissolution profiles. On the contrary, formulations and dissolution conditions would have minimal effects on the dissolution profiles of a fast-dissolving solid dispersion. CONCLUSIONS: Different techniques are available to select the right polymers to optimize dissolution behaviors. However, it is important to understand the merits and limitations of each technique in order to optimize the formulations for amorphous solid dispersions.

Oral delivery of poorly soluble compounds by supersaturated systems.

"New formulation and manufacturing methods are now available to efficiently and effectively increase solubility and maintain the supersaturation of a thermodynamically metastable state".

Investigation of drug delivery by iontophoresis in a surgical wound utilizing microdialysis.

PURPOSE: This study investigated the penetration of lidocaine around and through a sutured incision following the application of iontophoretic and passive patches in the CD Hairless rat. MATERIALS AND METHODS: Concentrations in localized areas (suture, dermis, subcutaneous, and vascular) were determined using microdialysis sampling followed by analysis using liquid chromatography with UV detection. RESULTS: Iontophoresis significantly enhanced the dermal penetration of lidocaine. In an intact skin model, dermal concentrations were 40 times greater following iontophoretic delivery compared to passive delivery. In a sutured incision model, iontophoresis enhanced localized concentrations in the dermis, suture, and subcutaneous regions by 6-, 15-, and 20-fold, respectively. Iontophoretic delivery to a region containing a sutured incision was focused to the incision resulting in a greater increase in the suture concentration and in the subcutaneous region directly below the incision. CONCLUSIONS: The four microdialysis probe design was successful in the determination of localized drug penetration in a sutured incision model. Iontophoresis enhanced skin penetration and allowed for site specific delivery when applied to a sutured incision.

The application of ink-jet technology for the coating and loading of drug-eluting stents.

The combination of drugs with devices, where locally delivered drugs elute from the device, has demonstrated distinct advantages over therapies involving systemic or local drugs and devices administered separately. Drug-eluting stents are most notable. Ink jet technology offers unique advantages for the coating of very small medical devices with drugs and drug-coating combinations, especially in cases where the active pharmaceutical agent is very expensive to produce and wastage is to be minimized. For medical devices such as drug-containing stents, the advantages of ink-jet technology result from the controllable and reproducible nature of the droplets in the jet stream and the ability to direct the stream to exact locations on the device surfaces. Programmed target deliveries of 100 microg drug, a typical dose for a small stent, into cuvettes gave a standard deviation (SD) of dose of 0.6 microg. Jetting on coated, uncut stent tubes exhibited 100% capture efficiency with a 1.8 microg SD for a 137 microg dose. In preliminary studies, continuous jetting on stents can yield efficiencies up to 91% and coefficients of variation as low as 2%. These results indicate that ink-jet technology may provide significant improvement in drug loading efficiency over conventional coating methods.